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  <CENTER>   <H3>Tool 11: Sniff and verify checksums</H3>
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  <P><H3>Description:</H3>
   <PRE>
  This tool sniffs and verify checksums (IP header, TCP, UDP, etc.).
  If a bad checksum is encountered, it is displayed along with the
  expected value.
  
  Parameter --device indicates on which device to sniff. Please note
  that under some systems, such as Windows, sniffing on some devices is
  not supported.
  Parameter --filter defines the sniff filter. It permits to restrict
  captured packets. This kind of filter is named a BPF or pcap filter.
  Basic elements of a filter are:
    host 1.2.3.4
    net 192.168.10
    net 192.168.10.0 mask 255.255.255.0
    net 192.168.10.0/24
    port 21
    dst host 1.2.3.4
    src port 2345
    ether host a:b:c:d:e:f ('ether a:b:c:d:e:f' is not working)
    ether src aa:bb:cc:dd:ee:ff
    ip
    arp
    rarp
    tcp
    icmp
    udp
  Here are filter examples:
    "host 1.2.3.4"
    "net 192.168 and icmp"
    "host 1.2.3.4 or dst port 80"
    "(udp or tcp) and not host 1.2.3.4"
  Parameter --rawip indicates to ignore Ethernet/link layer, and start
  displaying at IP header.
  Parameter --ipreas tries to reassemble IP packets. This might miss
  packets.
  
  This tool may need to be run with admin privilege in order to sniff.
   </PRE>

  <P><H3>Synonyms:</H3>
  &nbsp;&nbsp;capture<BR>

  <P><H3>Usage:</H3>
  &nbsp;&nbsp;netwox 11 [-d device] [-f filter] [-r|+r] [-i|+i]<BR>

  <P><H3>Parameters:</H3>
<TABLE BORDER=1 CELLPADDING=4>
 <TR>
  <TD ALIGN=middle><I>parameter</I></TD>
  <TD ALIGN=middle><I>description</I></TD>
  <TD ALIGN=middle><I>example</I></TD>
 </TR>
 <TR><TD><TT>-d|--device device</TD>
<TD>device name</TD>
<TD>Eth0</TD></TR>
<TR><TD><TT>-f|--filter filter</TD>
<TD>pcap filter</TD>
<TD>&nbsp;</TD></TR>
<TR><TD><TT>-r|--rawip|+r|--no-rawip</TD>
<TD>sniff at IP level</TD>
<TD>&nbsp;</TD></TR>
<TR><TD><TT>-i|--ipreas|+i|--no-ipreas</TD>
<TD>reassemble IP packets</TD>
<TD>&nbsp; </TD></TR>
</TABLE>

  <P><H3>Example:</H3>
  &nbsp;&nbsp;netwox 11<BR>
<BR>
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